Search Results (69)

Aircraft wing surface icing compromises flight safety, where accurate calculation of heat transfer coefficient on airfoil surfaces serves as a prerequisite for designing thermal anti-icing systems. However, during icing conditions, ice morphology changes wall roughness and transition properties, making it difficult to accurately determine the heat transfer coefficient. The current study develops a partitioned rough-wall boundary layer integral methodology in order to overcome this issue, extending the conventional boundary layer integral method. The technique generates a convective heat transfer coefficient formulation for aircraft icing surfaces while accounting for roughness differences brought on by water droplet shape. The results show that the partitioned rough-wall boundary layer integral method divides the wing surface into three distinct zones based on water droplet dynamics—a smooth zone, rough zone, and runback zone—each associated with specific roughness values. The NACA0012 airfoil was used for numerical validation, which showed that computational and experimental data concur well. Additionally, the suggested approach predicts transition locations with a high degree of agreement with experimental results. Full article

Electret filter media are electrostatically charged during the manufacturing process to activate effective electrical separation mechanisms. In order to investigate the influence of humidity on these mechanisms, the electric field, and filtration efficiency, a Direct Numerical Simulation (DNS) study of the aerosol deposition within wetted fibrous nonwoven filter media used in masks was carried out. Initial experimental investigations determined key properties of the filter material, including porosity, fiber diameter, and surface charge density. Using Micro-Computed Tomography (µCT), preferred locations for droplet deposition within the filter were identified. Additional experiments quantified the amount of water absorbed by the filter medium and assessed its impact on the existing electric field. Numerical simulations examined various models with differing porosity and fiber diameter, incorporating different levels of water content to analyze the changes in the electric field, flow velocity, and resulting filtration efficiency. The results provide valuable insights into the significant effects of fiber change on filtration performance, demonstrating the electret filter’s ability to partially compensate for the negative impacts of water. Full article

The cryopreservation of limited sperm samples, especially those retrieved from patients, poses significant challenges due to the small number of viable cells available for freezing. Traditional microliter cryopreservation methods are fraught with difficulties, as thawed sperm cells become nearly impossible to locate under a microscope due to their mobility and the multiple focal planes presented by larger drops. This search time is critical, as sperm cells enter a state of decline post thaw. Conversely, when sperm cells are cryopreserved in nanoliter volumes, they can be easily discovered but do not survive the freezing and thawing processes entirely. This phenomenon is attributed to the diffusion of water molecules from the droplet into the surrounding oil, which, while designed to limit evaporation, inadvertently increases solute concentrations in the aqueous environment, leading to cellular desiccation. This article elucidates the mechanisms underlying this lethal diffusion effect and presents a novel approach for freezing in nanoliter volumes, which has demonstrated significantly improved survival rates through carefully optimized procedures in clinical trials. Our findings highlight the importance of adapting cryopreservation techniques to enhance the viability of individual sperm cells, ultimately facilitating better outcomes in assisted reproductive technologies. This study provides the first quantification of nanoscale water diffusion dynamics during cryopreservation, establishing a predictive model that explains the catastrophic loss of sperm viability and identifying the critical role of water diffusion as a major impediment for limited samples. The novelty of our results lies in both elucidating this specific mechanism of cell death and introducing a novel approach: utilizing water-saturated oil as a protective layer. This method effectively mitigates the osmotic stress caused by water loss, demonstrating remarkably improved cell survival. This work not only advances the scientific understanding of cryopreservation at the nanoscale but also offers a practical, impactful solution poised to revolutionize fertility treatments for patients with low sperm counts and holds promise for broader applications in biological cryopreservation. Full article

Ice accumulation on cold surfaces presents significant operational and safety challenges in various fields such as power transmission, aviation, and polar marine transportation. This study investigates the effectiveness of selectively applied superhydrophobic patterns on hydrophilic substrates to locally control freezing behaviors. The freezing dynamics of water droplets impacting surfaces with hybrid wettability patterns were investigated experimentally under cold conditions. The results demonstrate that superhydrophobic surfaces significantly reduce the freezing rate due to decreased contact time and the contact region. By selectively placing superhydrophobic patterns on hydrophilic surfaces, the location of ice formation could be effectively manipulated. The use of multiple superhydrophobic stripes was found to segment the impacting droplets into several parts, implying the ability to selectively avoid ice accumulation at specific areas. Furthermore, experiments identified critical temperature thresholds at which the effectiveness of superhydrophobic stripes diminishes. When the temperature of the substrate is higher than −25 °C, the superhydrophobic stripes can sufficiently divide an impacting droplet leaving no ice at the superhydrophobic region. In the tested temperature range between −25 °C and −40 °C, the ice coverage ratio at the superhydrophobic region increases as temperature decreases, with a maximum value of 25.6 ± 2.33% at −40 °C. Superhydrophobic patterns also exhibited improved deicing efficiency during melting processes, highlighting their potential for robust ice management applications. Full article

With the widespread application of ozone technology in agricultural plant protection, developing an ozonated water atomizer that integrates efficient mixing and precise spraying has been recognized as a significant challenge. Swirling flow is considered a method to enhance hydrodynamics and mass transfer in gas–liquid mixing. This study innovatively combines an axial nozzle with a swirling mixing chamber, utilizing the negative pressure generated by the high-speed central airflow at the nozzle throat as the driving force for swirling mixing and initial atomization, completing mass transfer and preliminary atomization before the formation of the mist, thereby improving gas–liquid contact and mass transfer efficiency. Through numerical simulations, the impact of geometric parameters at key locations on the internal flow of the atomizer was analyzed. The optimized inlet diameter of the atomizer was found to be 9 mm, with a throat length of 3 mm and a self-priming hole diameter of 1.5 mm. Experimental results on droplet size and ozone droplet concentration verified that at the optimal spraying pressure of 0.6 MPa, a concentration of up to 3.73 mg·L⁻¹ with an average droplet size of 102 µm, evenly distributed, could be generated at a distance of 40 cm from the target. This work provides a technological framework for advancing precision ozone-based plant protection, aligning with global efforts to reduce agrochemical footprints through innovative application systems. It offers theoretical guidance and data support for the development and design of high-efficiency ozone atomizers in agricultural applications, aiming to minimize the use of agricultural chemicals and promote the growth of green plant protection technologies. Full article

The research and development of a matrix of Addressable Nanoliter Containers (ANLCs) is the focus of this work. ANLCs introduce a novel approach for cryopreserving single sperm cells. A significant increase in sperm cell mortality was observed after cryopreserving nanoliter-scale cell suspensions, attributed to the diffusion of water from the aqueous droplets into the surrounding oil phase. This process elevated the salt concentration within the droplets. A practical solution was devised by saturating the oil with water, significantly reducing the concentration gradient and, consequently, the diffusion. For ANLCs smaller than a few nanoliters, locating individual sperm cells within the containers became highly feasible. Using saturated oil, the survival rate reached 100%. Optical simulations were conducted to evaluate the impact of ANLCs on light scattering, enabling the selection of designs with minimal scattering. The simulations conclusively demonstrated that a cylindrical container with a flat bottom produced the least light scattering. This device was tested under clinical conditions in an in vitro fertilization (IVF) laboratory, revealing its strong potential as a practical tool for housing individual sperm cells. It enables characterization using interferometric indicators and facilitates the selection of sperm cells for IVF. Full article

Precision pesticide application mainly relies on canopy volume, resulting in varied application effectiveness across different density areas of orchard trees. This study examined pesticide application effectiveness based on the spray wind, canopy volume, and leaf area within the canopy, providing variable bases for precise regulation of spray wind and pesticide dosage. The study addresses the knowledge gap by utilizing laser detection and ranging (LiDAR) to measure the thickness and leaf area of orchard tree canopies. The spray experiments were conducted on canopies of different regions, using an air-assisted sprayer with varying fan speeds of 1381 r/min, 1502 r/min, and 1676 r/min. The deposition effects were analyzed using water-sensitive papers. The inlet air speed within the canopy did not increase proportionally when the spray fan speed increased, and it showed a significant variation in locations with sparse foliage. Furthermore, droplets exhibited abnormal median volume diameters of the canopy regions with lower wind loss rates and smaller leaf areas. The influences were in the order of canopy thickness, leaf area, and inlet air speed on the cumulative deposition of droplets on both sides of the water-sensitive papers, as well as the ratio of deposition between the two sides, from big to small, are inlet air speed, leaf area, and canopy thickness. The study provides a scientific foundation for air control in precision pesticide application in apple orchards and contributes to the rapid development of precision spraying technologies. Full article

Plasmopara viticola is the causal agent of Grapevine Downy Mildew (GDM), which is a devastating disease of grapevines in humid temperate regions. The most employed method for protecting grapevines against GDM is the application of chemical fungicides. In Spain, Carboxylic Acid Amides (CAAs) are a fungicide group currently utilized in GDM control. In P. viticola, resistance to CAAs is conferred by G1105S and G1105V mutations in the CesA3 gene. Droplet digital polymerase chain reaction (ddPCR) is an innovative technique that combines PCR and droplet microfluidics to disperse the sample into thousands of water-in-oil droplets in which an amplification reaction is individually performed. In this study, we set up a ddPCR protocol to quantify S1105 and V1105 mutations conferring resistance to CAAs in P. viticola. The optimal PCR conditions were established, and the sensitivity and precision of the protocol were assessed. Four P. viticola populations coming from commercial vineyards in northern Spain were analyzed, and different allele frequencies were found in the analyzed samples corresponding to the different fungicide management strategies, ranging from 7.72% to 100%. Knowing the level of mutated alleles allows for designing resistance management strategies suited for each location. This suggests that similar ddPCR assays could be developed for studying mutations implicated in fungicide resistance in other fungicide groups and plant pathogens. Full article

Curcumin is a hydrophobic bioactive compound, and its incorporation into lipid-based carriers can enhance its bioaccessibility and maintain its stability over time. Pickering emulsions are long-term stability systems, effective for encapsulation, protection, and delivery of bioactive compounds. This study aimed to produce Pickering oil-in-water (O/W) emulsions stabilized by cassava starch nanoparticles (native or modified by heat–moisture treatment (HMT)) with high kinetic stability to encapsulate curcumin. The effect of curcumin incorporation on emulsion features was also assessed, as well as curcumin stability over time. Native starch nanoparticles (NSNPs) were not effective stabilizers in the concentration range of 0.8 to 4 wt%. Otherwise, modified starch nanoparticles (HSNPs) at 4 wt% produced a long-term stability Pickering emulsion, which was used to encapsulate curcumin (0.07 wt%). Confocal laser scanning microscopy (CLSM) showed that HSNPs were located at the droplet’s interface. The interfacial tension for HSNPs exhibited initial values from 40 to 33 mN/m, quickly reaching equilibrium. These findings suggest that HSNPs exhibit low surface activity and the stabilization mechanism of emulsion is based on steric hindrance. The stabilization by steric hindrance is supported by the low zeta potential value (−5.39 mV). Stable emulsions showed shear thinning behavior, and the power-law model demonstrated excellent fit to experimental data (R² ≥ 0.998). The addition of curcumin reduced the interfacial tension, droplet size, apparent viscosity, and consistency index, indicating that this bioactive compound can also act at the interface. After 60 days, curcumin degradation was fully avoided. Our findings indicated that HSNP-stabilized Pickering emulsions can protect encapsulated curcumin from degradation. Full article

The flow and morphological characteristics of liquid water on the icing and anti-icing surfaces of aircraft are closely related to the icing characteristics and anti-icing surface temperature distribution. To predict the flow and breakup characteristics of a water film, a 3D model of continuous water film flow and a model of water film breakup into rivulets on an anti-icing surface were constructed based on the icing model, and the corresponding methods for solving the models were developed. Using the NACA0012 airfoil as a simulation object, the changing characteristics of height and velocity for a continuous water film with time and the morphological characteristics of rivulets formed from the breakup of a continuous water film were simulated numerically. The results indicate that, with an increase in inflow velocity, the time required for the water film to completely cover the surface and reach stability decreases. Downstream in the water droplet impact zone, the calculated values of continuous water film height align well with experiments, as well as the stream height at the continuous water film rupture location with the experimental values. With the reasonable contact angle, the calculation error of the stream width is within 10%. Full article

The use of remotely piloted aircraft (RPA) to spray pesticides currently occurs, but knowledge about this technology is lacking due to the different locations, targets, and products applied. The objective of this study was to evaluate the control of Urochloa decumbens with glyphosate applied using an RPA (10 L ha⁻¹) equipped with different spray nozzles (XR 11001 and AirMix 11001). For the purpose of comparison, ground application was also performed (100 L ha⁻¹). The deposition was evaluated by means of the quantification of a tracer by spectrophotometry, the droplet spectrum was evaluated with water-sensitive paper, and the control efficiency was evaluated based on visual measurements with percentage scores. Statistical process control was used to analyse the quality of the deposition in the area. The results showed that the application via RPA presented a greater amount of tracer on the leaves than the ground application, suggesting that the former is a good option for application, even providing a lower coverage and number of droplets per area. Both application methods were effective at controlling Urochloa decumbens. The nozzles showed potential for use in applications, with control efficiency higher than 84% from 21 days after application. The percentage of droplets smaller than 100 μm in the applications was less than 5%. No nonrandom behaviour was observed during deposition, indicating a high-quality process. Full article

Tow-dimensional and 3-dimensional colloidal structures have been used to study surface-enhanced Raman scattering and localized surface plasmon resonance because of their regular stacking structures. However, freely controlling the number and size of the colloidal assemblies remains a challenge. In this study, we demonstrated the fabrication and mechanism of tiny nanoclusters using spontaneous evaporation-based nanofountain pens (NFPs). A micrometer-scale NFP nozzle was fabricated using a glass capillary. The gold nanoparticles (AuNPs) dispersed ink formed the pendant droplet at the NFP nozzle tip, where the AuNPs accumulated within the pendant droplet because of evaporation. The accumulated AuNPs were transferred onto the substrate via a stamp-like process to create nanoclusters. Using water evaporation analyzed by diffusion equations, we showed that reducing the AuNP accumulation to one hundred is possible. This precise adjustment enables fabrication until submicrometer-level nanoclusters. The fabrication method using NFPs can create 3D structures, and this operation is not significantly affected by the size or composition of the AuNPs. This could be expanded to metabolite-included nanocluster where metabolite can be located at the hot spot among AuNPs. Therefore, we expect that this will be utilized to create SERS signals and conduct disease diagnosis research using extremely small amounts of metabolites. Full article

This paper presents an evaluation of a system aiming at estimating water depths on a road surface. Using accelerometers, the system records the vibrations of a wheel arch liner due to impacts of water droplets. The system setup, including the location of the accelerometers on a wheel arch and the data acquisition, is described. Tests were performed with a passenger car on various road surfaces and at different vehicle speeds and water depths. Signals recorded by the accelerometers are filtered and processed. The link between the acceleration amplitude, the water depth, and the vehicle speed is consistent with results from previous studies. The effect of the surface texture is less obvious and needs further investigations. A mathematical model has been developed to relate the acceleration amplitude to the water depth. The potential application of the developed system to on-board evaluation of pavement wetness, and consequently the pavement skid resistance, is discussed. Perspectives for driver assistance, or more generally, for autonomous driving to improve traffic safety, are also highlighted. Full article

Water-in-oil-in-water (W/O/W) emulsions with high-melting diacylglycerol (DAG) crystals incorporated in the oil droplets were fabricated and the compositions were optimized to achieve the best physical stability. The stability against osmotic pressure, encapsulation efficiency and in vitro release profiles of both water- and oil-soluble bioactives were investigated. The presence of interfacial crystallized DAG shells increased the emulsion stability by reducing the swelling and shrinkage of emulsions against osmotic pressure and heating treatment. DAG crystals located at the inner water/oil (W₁/O) interface and the gelation of the inner phase by gelatin helped reduce the oil droplet size and slow down the salt release rate. The DAG and gelatin-contained double emulsion showed improved encapsulation efficiency of bioactives, especially for the epigallocatechin gallate (EGCG) during storage. The double emulsions with DAG had a lower digestion rate but higher bioaccessibility of EGCG and curcumin after in vitro digestion. DAG-stabilized double emulsions with a gelled inner phase thus can be applied as controlled delivery systems for bioactives by forming robust interfacial crystalline shells. Full article

This study aims to fabricate zein-based colloidal nanoparticles, which were used to stabilize Pickering emulsions, by conjugation with soybean polysaccharide (SSPS) through the Maillard reaction. The physicochemical properties of the conjugated particles as well as the physical and oxidative stability of the fabricated Pickering emulsion that utilized conjugated colloidal particles with the volumetric ratio of water and oil at 50:50 were investigated. The grafting degree of zein and SSPS was verified through examination of FT-IR and fluorescence. Moreover, the conjugated Zein/SSPS nanoparticles (ZSP) that were prepared after dry heating for 48–72 h exhibit excellent colloidal stability across a range of pH values (4.0–10.0). Further, the wettability of ZSP decreased based on a contact angle analysis of θ~87°. Confocal laser scanning microscopy (CLSM) images indicated that ZSP particles were located around the oil droplets. Additionally, the ZSP effectively improved the oxidative stability of the Pickering emulsions, as demonstrated by a significant decrease in both peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). The results of this study demonstrate that ZSP represents a promising food-grade Pickering emulsifier, capable of not only stabilizing emulsions but also inhibiting their oil oxidation. Full article